1. Field of the Invention
The present invention relates to a lubricant composition, and more particularly, to a lubricant composition comprising a polyether compound having a good lubricating effect that can increase resistance to abrasion and reduce friction during frictional sliding.
The present invention further relates to a magnetic recording medium comprising a layer containing the above polyether compound, and a novel polyether compound.
2. Discussion of the Background
In recent years, the need for high-density recording has been increasing, and there is demand for a magnetic recording medium having good electromagnetic characteristics. However, when the smoothness of the magnetic layer surface is increased for high density recording, the increase in the coefficient of friction may compromise running properties and durability. Accordingly, various attempts to lower the coefficient of friction have been made by adding a lubricant to the magnetic layer and nonmagnetic layer in particulate magnetic recording media (for example, see Japanese Unexamined Patent Publication (KOKAI) No. 2008-239575 or English language family member US 2008/0241599 A1 and Japanese Unexamined Patent Publication (KOKAI) No. 2008-7469 or English language family member US 2008/0020243 A1), and by coating a lubricant on the magnetic layer in a thin-film magnetic recording medium to form a lubricant film (for example, see Japanese Unexamined Patent Publication (KOKAI) Heisei No. 7-138586). The contents of the above publications are expressly incorporated herein by reference in their entirety.
In the above publications, carbonic acid ester compounds are proposed as lubricants. For reasons such as the fact that carbonic acid ester compounds have low melting points and the carbonic acid ester moiety contributes to resistance to hydrolysis, they are known to exhibit good lubricating properties in magnetic recording media.
However, as the result of examination conducted by the present inventors, the followings were found with carbonic acid ester-based lubricants that are widely employed in conventional magnetic recording media:
(1) The carbonic acid ester group is of low polarity, tending not to conform to metals. Thus, the film strength is weak when applied as a lubricant film to the surface of a metal.
(2) In particulate magnetic recording media, compounds of high polarity, such as polyurethane and vinyl chloride resins are generally employed. Additionally, in the above carbonic acid ester lubricants, hydrophobic compounds such as long-chain alkyls are employed, resulting in poor compatibility with binder. When the quantity of a lubricant with poor compatibility is increased, there is a concern that crystallization will end up occurring on the surface of the magnetic layer, and when running is temporarily stopped while in a state of contact with the head member, there is concern that the lubricant will gradually bleed out onto the surface of the medium while running is stopped, resulting in the head member adhering to the medium surface when running is resumed and thus generating considerable startup friction (running durability decreases).